In general, in a fuel cell power generating apparatus which utilizes hydrogen obtained by reforming, for instance, a hydrocarbon with a fuel reforming apparatus, particularly a small-sized AC fuel cell power generating apparatus for supplying power to an electric power load which causes vigorous variation, it is required to increase or decrease the feed rate of a starting material to be reformed such as hydrocarbons, which is fed to the fuel reforming apparatus, and that of a fuel air to be fed to the fuel cell portion depending on the increase or decrease of the electric power load.
In addition, a reforming catalyst for promoting a reforming reaction is filled in the fuel reforming apparatus and, therefore, a fuel for heating the reforming catalyst must be used. The feed rate of auxiliary combustion air for burning the fuel for heating must also be increased or decreased depending on the increase or decrease in the feed rate of the fuel for heating. In the fuel reforming apparatus, it is necessary to maintain the temperature in the reforming apparatus at a predetermined level to increase reforming efficiency of a starting material to be reformed and a extend the life time of the reforming catalyst.
On the other hand, the fuel cell portion suffers from a loss L represented by the following equation (1): EQU L=KI.sup.2 ( 1)
wherein I is an electric current outputted from the cell portion and K represents a proportionality factor.
Since the temperature of electrodes rises due to the loss L, usually the electrodes of the fuel cell are cooled with air so as not to cause an extreme increase in their temperature. Moreover, since, in the fuel cell portion, the temperature of the cell electrodes must be held at a predetermined level for achieving a good power generation efficiency, the fuel cell power generating apparatus should be controlled so that an electric current outputted from the cell portion and the feed rate of air for cooling the fuel cell portion are increased or decreased depending on the increase or decrease in the temperature of the fuel cell portion.
However, a conventional small-sized AC-fuel cell power generating apparatus for supplying electric power to an electric load which causes vigorous variation as in, for instance, a heater or an inverter air conditioner is not provided with a function for automatically increasing or decreasing the feed rate of a starting material for reforming and that of air to be fed to various apparatuses depending on the increase or decrease in the electric load or the like. Therefore, the conventional fuel cell power generating apparatus exhibits low load follow-up properties.
When the fuel cell is started and the electric load is in a very low level of the order of zero load such as those observed when a load is reduced to a low level, a current inversely passes through the fuel cell if the voltage of the electrodes of the fuel cell portion becomes extremely high. Therefore, another serve problem of deteriorating the electrodes, for instance, corrosion of an electrode catalyst such as platinum arises.